1. Field of the Disclosure
The present application generally relates to power efficient semiconductor design and, more specifically, to systems and methods for isolating power domains within integrated circuits.
2. Description of Related Art
In many electrical devices, and especially mobile devices, power consumption of the associated integrated circuits is a major design consideration. This power consumption primarily comprises switching current that results from actively functioning circuitry and leakage current that results from inactive circuitry passively drawing power.
As integrated circuit fabrication technology continually improves and migrates to smaller geometry, the size of transistors (e.g., their minimum channel length) continues to shrink. Additionally, the threshold voltage for smaller-size transistors, which is the voltage at which a transistor turns on, is often reduced to improve operating speed. The lower threshold voltages permit reductions in the power supply voltage, which in turn may reduce power consumption. But, the lower threshold voltages and smaller-size transistors can also lead to higher leakage currents, where “leakage” currents are, e.g., currents passing through transistors that are in an “off” state. Such leakage currents generally become more problematic as integrated circuit transistors continue to scale down in size. One technique to decrease leakage current is powering off certain portions of the integrated circuit when these portions are not in use. This technique is sometimes referred to as “power collapse.”
To implement power collapse, an integrated circuit is generally organized into a plurality of power domains, where each power domain may contain one or more processing nodes, peripherals, and/or other circuitry. Power domains may have varying voltage levels from each other, and different power domains may also have asynchronous clocks. In general, each power domain is individually controllable, such that one power domain may be power collapsed during a time when other power domains remain active.
During operation, circuitry within one power domain may need to communicate with circuitry in another power domain. Often, the different power domains also correspond to different clock domains, leading to clocking concerns at the boundaries between the domains. Accordingly, systems may need a cross-domain interconnect and protocols for data to flow between different power domains. Current protocols, such as the Advanced Extensible Interface (AXI) set forth by the Advanced Microcontroller Bus Architecture (AMBA), provide signaling and certain other aspects of an interconnect.